1 /* Copyright (c) 2006-2021. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #ifndef SIMGRID_S4U_SEMAPHORE_HPP
7 #define SIMGRID_S4U_SEMAPHORE_HPP
9 #include <simgrid/forward.h>
14 /** @brief A classical semaphore, but blocking in the simulation world
17 * It is strictly impossible to use a real semaphore, such as
18 * `sem_init <http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html>`_,
19 * because it would block the whole simulation.
20 * Instead, you should use the present class, that offers a very similar interface.
22 * An example is available in Section :ref:`s4u_ex_IPC`.
24 * As for any S4U object, you can use the :ref:`RAII idiom <s4u_raii>` for memory management of semaphores.
25 * Use :cpp:func:`create() <simgrid::s4u::Mutex::create()>` to get a :cpp:type:`simgrid::s4u::SemaphorePtr` to a newly
26 * created semaphore, that will get automatically freed when the variable goes out of scope.
30 class XBT_PUBLIC Semaphore {
32 friend kernel::activity::SemaphoreImpl;
33 friend void kernel::activity::intrusive_ptr_release(kernel::activity::SemaphoreImpl* sem);
36 kernel::activity::SemaphoreImpl* const pimpl_;
38 friend void intrusive_ptr_add_ref(const Semaphore* sem);
39 friend void intrusive_ptr_release(const Semaphore* sem);
41 explicit Semaphore(kernel::activity::SemaphoreImpl* sem) : pimpl_(sem) {}
42 ~Semaphore() = default;
44 Semaphore(Semaphore const&) = delete; // No copy constructor. Use SemaphorePtr instead
45 Semaphore& operator=(Semaphore const&) = delete; // No direct assignment either. Use SemaphorePtr instead
49 /** Constructs a new semaphore */
50 static SemaphorePtr create(unsigned int initial_capacity);
53 bool acquire_timeout(double timeout);
55 int get_capacity() const;
56 bool would_block() const;
60 } // namespace simgrid
62 #endif /* SIMGRID_S4U_SEMAPHORE_HPP */